In the CDMA2000 1X system, code division multiple access mode is used between physical channels, and different physical channels use different Walsh codes. All the physical channels under the same cell use a common PN short code, the common channels use a determined long code, and the dedicated channels use different long codes.
The same cell can use a carrier frequency which contains a plurality of different physical frequencies. In order to allocate channel resources rationally and high efficiently, an algorithm for the terminal to select the carrier frequency is defined in the 3rd Generation Partnership Project (abbreviated as 3GPP) 2 C.S0005 V3.0 protocol, in which the international mobile subscriber identity (abbreviated as IMSI) and the number of carrier frequencies are used as two operation parameters to obtain the frequency which is finally selected by the terminal.
3 Gpp2 C.S0005 V3.0 provides that the same frequency point can contain a plurality of different paging channels (7 at most) and rapid paging channels (3 at most). An algorithm for the terminal to select a paging channel sequential number or rapid paging channel sequential number is defined in 3 Gpp2 C.S0005 V3.0, in which the paging channel sequential number (or rapid paging channel sequential number) which is finally monitored by the terminal is obtained according to the IMSI and the number of paging channels (or the number of rapid paging channels).
In the CDMA system, as to the standby state, the terminal may work under two states, the non-slot state and the slot state. As to the non-slot state, the terminal monitors all the slots of the paging channel or rapid paging channel at the current frequency; as to the slot state, the terminal only demodulates a paging channel message (including a rapid paging channel message) in the slot which is agreed with the network and does not modulate in other slots, so that the object of saving batteries can be achieved. It is further needed to note that the subscriber will judge whether the network requires the terminal to monitor the rapid paging channel according to an overhead message sent by the network. If it is needed to monitor the rapid paging channel, then the subscriber will first demodulate relevant bits of the rapid paging channel under the slot state, and monitor the paging channel only in the situation that the paging indication bit is activated. If the network does not require monitoring the rapid paging channel, then it directly monitor the paging channel. The periods of monitoring the paging channel or rapid paging channel are both determined according to the method of taking the minimum among the subscriber slot cycle index (abbreviated as SCI) and the network maximum slot cycle index. The algorithm of the monitoring slot needs to be obtained by combining with the slot cycle index of the terminal and IMSI and the maximum slot cycle index of the network, according to the algorithm defined in 3 Gpp2 C.S0005 V3.0.
Rapid paging channel is defined in 3 Gpp2 C.S0005 V3.0. The terminal monitors a corresponding paging channel according to the paging indication bit, thus achieving the object of further saving the electricity of the terminal battery. The corresponding location algorithm of the paging indication bit is defined in 2.6.7 of 3 Gpp2 C.S0005 V3.0, and the paging indication location which needs to be monitored by the terminal can be obtained according to the subscriber IMSI, current system time, and the rate of paging channel.
Dual treats mobile phones (two GSM cards) of global system for mobile communication (abbreviated as GSM) have become very popular, and many GSM dual treats mobile phones can be found on the market. However, the situation of CDMA is different. Currently, still no mature CDMA dual treats solution appears, since the currently available CDMA mobile phone chip only contains one set of transmitter and receiver, while to achieve dual treats, the data of two subscribers needs to be monitored. According to the currently available CDMA protocol, it is limited that each receiver only has the capability of demodulating one frequency point. Therefore, achieving CDMA dual treats can be achieved only by the manner of setting two CDMA chips for scheduling.
The inventors have found that: currently, the single-mode chip only has the capability of demodulating one frequency point in one slot, therefore in the situation that dual treats are achieved on one single-mode chip, if the slots of these two subscribers are the same but the frequency points are different, then these two subscribers cannot demodulate the frequency points. This problem obstructs the implementation of dual treats in the CDMA system.